The present invention relates generally to an intake system intercommunicating a carburetor or carburetors and a combustion chamber or chambers of internal combustion engines, and more particularly to an improvement of an intake system for ensuring the complete combustion of the mixture fed from the carburetors.
In the conventional intake systems of the internal combustion engines, one intake manifold whose one end is connected to the carburetor is branched depending upon the number of cylinders of an internal combustion engine to be communicated with them so that the air-fuel mixture may be charged into the combustion chambers. A part of the intake manifold is exposed to the exhaust gases or cooling water so that the vaporization of the atomized fuel particles in the mixture may be facilitated. In this conventional arrangement, the heat of the exhaust gases or cooling water is indirectly transferred to the mixture traveling through the intake manifold so that the atomized fuel particles in the mixture are not efficiently vaporized. As a result, when the engine is started so that the temperature of the exhaust gases or cooling water is low, liquid fuel is charged into the combustion chambers. Therefore, the distribution among the combustion chambers or cylinders of a multicylinder engine is not satisfactory, and the engine operation is adversely affected when the engine is accelerated or decelerated. In some cases, the very rich mixture must be fed in order to restore the normal engine operation, thus resulting in the discharge of exhaust gases in large quantity. There has been also proposed to install the whole intake manifold within the exhaust manifold so that the mixture flowing through the intake manifold may be highly heated, but this arrangement has a distinct defect that the mixture is overheated in case of the engine operation under a heavy load, resulting in the decrease in engine output. In order to ensure the optimum engine operation, the temperature of the mixture charged into the combustion chambers must not be so high, and the atomized fuel particles in the mixture must be completely vaporized. However, any prior art intake systems cannot satisfactorily solve these problems.